This invention relates to a blind bolt fastener installation tool of the general class exemplified by the tools disclosed in U.S. Pat. No. 3,128,655, issued to Ben C. Keasler, entitled "Blind Bolt Installation Tool With Preloaded Torque-Responsive Driving Mechanism" and U.S. Pat. No. 2,789,597, issued to Joseph LaTorre, entitled "Driving And Setting Tool for Blind Fasteners". More particularly, it relates to an improved blind bolt fastener installation tool with an apparatus for retrieving blind bolt fastener stems which are severed during the installation of such fasteners. Still more particularly, it relates to an apparatus, which retrieves severed blind bolt fastener stems, for use in conjunction with a conventional blind bolt fastener installation tool.
Blind bolt fasteners are generally used to join sheets of work, such as metal sheets, in the fabrication of various products, such as airplanes. The fasteners are comprised of a screw portion, a nut portion and a collar portion. The screw portion has a generally circular head and a shaft, the shaft having external threads and wrenching flats. The end portion of the shaft is known as a break-off stem because it is severed from the shaft during the installation of the fastener, as will be explained below. The nut portion of the fastener usually has a section in the shape of a nut with a sleeve section extending therefrom, both the nut-shaped section and sleeve section having internal threads. The outside diameter of the sleeve section is approximately the same as the diameter of the head of the screw portion, and the width across the flats of the nut-shaped section is approximately twice the outside diameter of the sleeve section. The end of the sleeve section unattached to the nut-shaped section generally has a tapered end. The collar portion of the fastener is a hollow cylindrical piece having an outside diameter slightly less than or equal to the outside diameter of the head of the screw portion of the fastener and an inside diameter greater than the diameter of the shaft of the screw portion, the collar being constructed of a malleable metal.
A pre-installed blind bolt fastener has the shaft of its screw portion threaded through the sleeve and nut-shaped sections of its nut portion, with the shaft protruding a short distance through the nut-shaped section. The collar loosely fits around the shaft between the head of the screw portion and the tapered end of the sleeve section of the nut portion.
During the installation process, blind bolt fasteners are normally hand-loaded one at a time by the operator of the installation tool. They are loaded with the nut-shaped part of the nut portion being received and prevented from rotating by a cavity, called wrenching jaws herein, located at the forward end of the tool. The protruding part of the shaft passes through the wrenching jaws and is received by a rotating assembly having wrenching flats that mate with the flats of the shaft. The rotating assembly is located rearwardly of the wrenching jaws and adjacent thereto.
After the blind bolt fastener has been loaded in the foregoing manner, the operator places the part of the fastener projecting from the forward end of the installation tool through adjacent holds which have previously been drilled through the sheets of work to be joined. These holes are drilled with a diameter great enough to receive the head and collar portions of the fastener, as well as the shaft section of the nut portion, but with a diameter less than the width across the flats of the nut-shaped section of the nut portion. Also, a fastener is selected with a sleeve section of slightly greater length than the combined length of the adjacent holes in the work to be joined, such that when the operator gets the loaded fastener and tool in the ready position (i.e. with the nut-shaped section of the nut portion flush against the sheet of work nearest the tool), the head, collar and a short length of the shaft section extend beyond the sheet of work non-adjacent the tool.
When the operator has the fastener and tool in the aforementioned ready position, he starts the installation tool, causing the rotating assembly mentioned above and the protruding part of the shaft received by it to rotate in such a manner as to cause the shaft to be drawn rearwardly into the installation tool. This, of course, causes the head of the screw portion of the fastener to be drawn against the collar portion, with the collar, in turn, being forced over the tapered end of the sleeve section of the nut portion. The collar portion ultimately directly abuts the sheet of work non-adjacent the tool and is compressed and flattened such that the sheets of work are held securely between the nut-shaped section of the nut portion of the fastener and the flattened collar.
As the collar is compressed and flattened in the foregoing manner, a turning resistance in the shaft of the screw portion of the fastener builds up until the end portion, or break-off stem, of the shaft is twisted off and thereby severed from the fastener.
Conventional blind bolt installation tools are of a type which dispells the stem of a blind bolt fastener that is severed during the installation of the fastener. Normally, the severed stems are dispelled from the orifice into which the fastener is loaded prior to installation. Generally, this dispelling is facilitated by a spring, included within the rotating assembly mentioned above, which is contacted and compressed by the end portion of the fastener shaft as it is drawn into the tool during installation of the fastener. Hence, when the stem of the fastener is severed and the tool withdrawn from the fastened work, the severed stem is ejected from the tool by the expansion of the spring.
In practice, the severed blind bolt fastener stems dispelled from installation tools of the type referred to above are strewn around the working area of the operator of the installation tool to be cleaned up at some later time, unless they are manually collected by the operator, a process which is extremely time consuming. However, unless an operator carefully collects these severed stems, they create a potential safety hazard due to people stepping thereon and possibly slipping. Furthermore, they create another particularly acute problem in the airplane manufacturing industry, where blind bolt fasteners are used extensively for assembly purposes. During the assembly of airplanes, foreign matter of all types, particularly small metal pieces, such as severed blind bolt fastener stems, should be scrupulously collected by workers, such as operators of blind bolt fastener installation tools, due to the danger that they might ultimately become engaged in some vital part of an aircraft and cause a malfunction thereof. Hence, it would be highly advantageous to have a blind bolt installation tool with the facility for retrieving the severed stems of blind bolt fasteners before they are strewn about a particular working area.
It is an object of the present invention to provide an improved blind bolt fastener installation tool which is capable of retrieving the stems of blind bolt fasteners which are severed during the installation of such fasteners.
Another object of the present invention is to provide a method and an apparatus for retrieving severed blind bolt fastener stems which can be employed in conjunction with conventional type blind bolt fastener installation tools.
Still another object of the present invention is to provide for a simple and efficient means of retrieving severed blind bolt fastener stems normally ejected during operation of a blind bolt fastener installation tool.
Many other features, advantages and additional objects of the present invention will become manifest to those versed in the art upon making reference to the detailed description which follows and the accompanying sheets of drawings in which a preferred structural embodiment incorporating the principles of the present invention is shown by way of illustrative example only.